Add dnf bucket

This patchset adds dnf as a bucket.
Adds the keepcache line if it is not found in dnf.conf.

Signed-off-by: raghavendra talur <raghavendra.talur@gmail.com>

lib/vagrant-cachier/bucket.rb

@@ -102,3 +102,4 @@ require_relative "bucket/npm"
 require_relative "bucket/zypper"
 require_relative "bucket/generic"
 require_relative "bucket/pip"
+require_relative "bucket/dnf"

lib/vagrant-cachier/bucket/dnf.rb

@@ -0,0 +1,29 @@
+module VagrantPlugins
+  module Cachier
+    class Bucket
+      class Dnf < Bucket
+        def self.capability
+          :dnf_cache_dir
+        end
+
+        def install
+          if guest.capability?(:dnf_cache_dir)
+            guest_path = guest.capability(:dnf_cache_dir)
+            return if @env[:cache_dirs].include?(guest_path)
+
+            # Ensure caching is enabled
+            if !comm.sudo("grep -q 'keepcache=' /etc/dnf/dnf.conf", error_check: false)
+              comm.sudo("sed -i 's/keepcache=0/keepcache=1/g' /etc/dnf/dnf.conf")
+            else
+              comm.sudo("echo 'keepcache=1' >> /etc/dnf/dnf.conf")
+            end
+
+            symlink(guest_path)
+          else
+            @env[:ui].info I18n.t('vagrant_cachier.skipping_bucket', bucket: 'Dnf')
+          end
+        end
+      end
+    end
+  end
+end

lib/vagrant-cachier/cap/redhat/dnf_cache_dir.rb

@@ -0,0 +1,13 @@
+module VagrantPlugins
+  module Cachier
+    module Cap
+      module RedHat
+        module DnfCacheDir
+          def self.dnf_cache_dir(machine)
+            '/var/cache/dnf'
+          end
+        end
+      end
+    end
+  end
+end

lib/vagrant-cachier/capabilities.rb

@@ -61,6 +61,11 @@ module VagrantPlugins
         Cap::RedHat::YumCacheDir
       end
 
+      guest_capability 'redhat', 'dnf_cache_dir' do
+        require_relative 'cap/redhat/dnf_cache_dir'
+        Cap::RedHat::DnfCacheDir
+      end
+
       guest_capability 'suse', 'yum_cache_dir' do
         # Disable Yum on suse guests
       end